Any battery consists of two electrodes, an anode and a cathode, and some form of electrolyte. The electrodes are typically made of electrochemically active materials. Electrolytes can be liquid, gel, or other materials capable of conducting electric current. Once the electrodes are immersed into the electrolyte, electrochemical reactions take place and current will flow upon connecting an external load between the electrodes.
Gas bubbles evolving from electrodes in batteries may be observed during charging and discharging. The phenomenon has been observed in lead-acid and Ni/Cd batteries for example. This gas evolution does not contribute to the intended energy storage and power generation by the battery. In fact, it may be detrimental to the proper functioning of the battery where the voltage should be determined only by the chemical energy of the reactants stored in the electrode materials. However, gases also have electrochemical potential. This fact may be used for making a battery in which immobilized gases stored in or at the electrodes are the working materials (reactants). Such a battery is called a gas battery, while a similar device that uses flowing gases as reactants is called a fuel cell.
The concept of a gas battery operating on immobilized gases as reactants during discharge was demonstrated by Sir William Grove in 1839. The same well-known experiment led later to development of the fuel cell which is fed by flowing gases as reactants. Grove's gas battery consisted of two platinum spiral electrodes immersed in sulfuric acid electrolyte. During battery charging, hydrogen was adsorbed on one electrode and oxygen on another. Grove's experiments laid the conceptual basis for the development of both the gas battery and the fuel cell. Thus far, only the fuel cell has become well-known as a potential highly efficient continuous power generator. The combination of materials used by Grove in his experiment was not suitable for development of a gas battery, that is, an energy generator based on storing gases as reactants, although the device he operated clearly demonstrated the concept of a highly efficient pulse-power generator. While some activity related to development of gas batteries was reported in the 1950-1960s, it never led to a commercial device because of inherent limitations of the electrode materials available at that time.